<blockquote><cite>Posted By: Benpointer</cite>Hi

On the Dealec website it says of the Itho Eco 4 "Suitable for New Build high and low rise residential buildings but NOT renovations." Given I'm doing a renovation, I just wondered if anyone knew why they say this ??</blockquote>

Ben, another issue with renovations is the difficulty of running the ducting where existing joists etc arnt big enough to cope with the penetrations. There is normally another way to run the ducts, but this might involve longer runs etc.

The Drexel und Weiss catalogue has a section on duct insulation:
http://www.drexel-weiss.at/HP/Upload/Dateien/Kap03_Systeme_08_EN.pdf

I think there's also some stuff on the PHI site. There is a paper by Feist et al that talks about it and about woodstoves in passivhaus. I'll try to post a ref if anybody's interested.

Insulation is to (a) reduce heat loss, so is normally used wherever there's a temp difference between pipe and ambient, (b) to stop condensation, especially on and in the unit itself (also depends whether unit is in heated space or not),
(c) reduce noise.

If you are heating the air in order to heat the house, then whether or not particular lengths of distribution duct are insulated depends on whether or not you want extra heat to leak into the room it is passing through. Professional modelling help is good at that level!

If you are doing a refurb, then MVHR may be overkill and apparently may not even perform as well as MEV, depending on airtightness levels achieved.

Cheers, Dave